An SF (Switch Fabric, switch fabric) is formed by multiple SEs (Switch Element, switch element) and FICs (Fabric Interface Chip, fabric interface chip). The SE and the FIC are located in a Switch Card (switch board or switch card for short) and an LC (Line Card, line card), respectively. An Ingress FIC (ingress fabric interface chip) in an Ingress LC (ingress line card) sends a data packet to the SE. Each SE can switch or distribute the received data packet to a connected next-level SE. The last-level SE sends the data packet to an Egress FIC (egress fabric interface chip) in an Egress LC (egress line card).
In a multi-level data switching system in the prior art, an FIC and an SE 1/3 are located in an LCC (Line Card Chassis, line card chassis), and SE 2 is located in an FCC (Fabric Card Chassis, fabric card chassis). Both working modes of an SE 1 and an SE 3 are integrated in the SE 1/3, and the two working modes coexist in the SE. In such a system, the FCC is generally connected to the LCC through a fiber or an electric cable. The SE 1 in the LCC distributes the packets, which are sent by the Ingress FIC, to different SEs 2 in the FCC; and the SE 2 switches the data packet into a destination LCC according to information carried in the data packet; finally, the SE 3 of the destination LCC switches the received data packet into the Egress FIC. Data packets between all the FICs in the system need to pass through SE 1, SE 2, and SE 3 in sequence before arriving at the Egress FIC.
In the foregoing multi-chassis data switch fabric, in order to implement cascading of multiple LCCs, a user needs to buy and configure the FCC, which increases costs.
In the prior art, two-chassis cascading may also be implemented through back-to-back interconnection of two LCCs directly. However, the cascading method is suitable for cascading of two chassis only, and cannot be used for cascading of three or more chassis.